The long range goal of this project is to uncover key mechanisms responsible for tumor cell invasion and metastasis. Information generated from this study will facilitate early detection methods and prognosis of aggressive human cancers, as well as contribute to novel therapeutic strategies. Indirect evidence from a few laboratories indicates a strong correlation between dual intermediate filament expression -- specifically cytokeratins and vimentin, and metastatic aggressiveness observed in human melanoma and breast cancer models. Recently, these studies have been extended to human B cell lymphoma, in addition to a mouse L cell model consisting of clones transfected with keratins 8 and 18. The latter model allowed unique observations related to cell spreading and motility, and posed several important questions which will be addressed in the present study. Specifically, this proposal will test the prediction that dual expression of cytokeratins and vimentin contributes to metastasis. In the performance of the proposed experiments, it is expected that a morphological connection will be established between the extracellular environment and the intermediate filaments, which will implicate the transduction of signals pertaining to positional cues, cell shape and ultimately motility. The general approach to be followed is to up-regulate and down-regulate dual intermediate filament gene expression in both human melanoma and breast cancer models, and observe the consequence(s) on cell motility, invasiveness and metastatic potential. Specific Aim #1: To test the prediction that human melanoma cells (which express primarily vimentin) will become more invasive and metastatic after transfection with keratins 8 + 18 CDNAS. Specific Aim #2: To test the prediction that human breast cancer cells (which express primarily cytokeratins) will become more invasive and metastatic after transfection with vimentin CDNA. Specific Aim #3: To test the prediction that suppression of cytokeratin expression in human melanoma, and vimentin expression in breast carcinoma models, will reduce their invasive and metastatic activity, respectively. Specific Aim #4: To test the prediction that cell shape and spreading ability on extracellular matrices are uniquely modulated as a consequence of additional intermediate filaments, and this dual expression underlies augmentation of metastatic potential.